Method for inspecting measurement object

ABSTRACT

An inspection method for inspecting a device mounted on a substrate, includes generating a shape template of the device, acquiring height information of each pixel by projecting grating pattern light onto the substrate through a projecting section, generating a contrast map corresponding to the height information of each pixel, and comparing the contrast map with the shape template. Thus, a measurement object may be exactly extracted.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of Korean PatentApplication No. 2009-60542 filed on Jul. 3, 2009, Korean PatentApplication No. 2010-8689 filed on Jan. 29, 2010 and Korean PatentApplication No. 2010-60945 filed on Jun. 28, 2010, which are both herebyincorporated by reference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Exemplary embodiments of the present invention relate to a method forinspecting a measurement object and, more particularly, to a method forinspecting a measurement object formed on a printed circuit board.

2. Discussion of the Background

In general, electronic appliances include at least one printed circuitboard printed circuit board (PCB), and various kinds of electronicdevices are mounted on the printed circuit board.

In order to check the credibility of a substrate having electronicdevices mounted thereon, inspecting the mounting status of theelectronic devices is required and it is important to setting up aregion of a measurement object.

Previously, in order to set up the region of a measurement object, a twodimensional image is captured to be used. However, setting up the regionof a measurement object from the two dimensional image is not easy sinceit is hard to discriminate the measurement object from environmentsbecause a device is sensitive to a color and an illuminator. When thedimension of the measurement object is changed, it is hard todiscriminate the measurement object. Furthermore, when the imagecontains a noise, for example, when not only the measurement object butalso a pattern or a silk screen pattern is formed on a substrate, it ishard to discriminate the measurement object since a noise may begenerated by a camera and the region of the measurement object may beconfused with a pad region adjacent to the region of the measurementobject. Additionally, a device has been extracted by using a filletportion of a two dimensional image of the device, but when the fillet ofthe device is small, there is a limitation in extracting the deviceusing the fillet.

Therefore, a new method for inspecting a three-dimensional shape, whichis capable of avoid above mentioned problems, is required.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention provide a method forinspecting a measurement object, capable of extracting a measurementobject exactly.

Additional features of the invention will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention.

An exemplary embodiment of the present invention discloses an inspectionmethod for inspecting a device mounted on a substrate. The inspectionmethod includes generating a shape template of the device, acquiringheight information of each pixel by projecting grating pattern lightonto the substrate through a projecting section, generating a contrastmap corresponding to the height information of each pixel, and comparingthe contrast map with the shape template.

The inspection method may further include acquiring at least oneinformation of a size, a position and a rotation of the devicecorresponding to the shape template by comparing the contrast map withthe shape template.

The projecting section may include a light source, a grating unitconverting light generated by the light source into the grating patternlight and a grating transfer unit transferring the grating unit. Theprojecting section may project the grating pattern light onto thesubstrate N-times, transferring the grating unit.

The inspection method may further include acquiring visibilityinformation of each pixel of the substrate through N-number of imagescaptured by a camera when the grating pattern light is reflected by thesubstrate. The contrast map may be defined by a value calculated bymultiplying the height information with the visibility information. Thevisibility information (Vi(x,y)) may be a ratio of amplitude (Bi(x,y))to average (Ai(x,y)) (or (Vi(x,y)=Bi(x,y)/Ai(x,y))) in intensity ofimage at each pixel.

The contrast map and the shape template may be compared with each otherwithin a specific tolerance value of the template.

Comparing the contrast map with the shape template may includemultiplying a value of zero or one in the shape template, which isallotted according to a coordinate of pixel with a contrast value of aregion where the contrast map overlaps with the shape template to getresult values, and summing up the result values, determining a positionwhere the sum of the result values becomes maximum to be a position ofthe device by moving the shape template, and confirming the device isthe device corresponding to the shape template when the maximum value isno less than a criterion.

Another exemplary embodiment of the present invention discloses aninspection method for inspecting a device mounted on a substrate. Theinspection method includes generating a shape template of the device,acquiring shadow information of each pixel by projecting light onto thesubstrate in a plurality of directions, generating a shadow map bymerging a plurality of shadow information taken in a plurality ofdirections, and comparing the shadow map with the shape template toacquire at least one information of a size, a position and a rotation ofthe device.

Acquiring shadow information of each pixel by projecting light onto thesubstrate in a plurality of directions may include projecting gratingpattern light onto the substrate in a plurality of directions N-times,while shifting a phase of the grating pattern light and capturingN-number of images reflected by the substrate.

Acquiring shadow information of each pixel by projecting light onto thesubstrate in a plurality of directions may further include averaging theN-number of images or summing up images in the N-number of images suchthat sum of phase differences of the images becomes 360 degrees, to getimages in which grating pattern is removed.

Still another exemplary embodiment of the present invention discloses aninspection method for inspecting a device mounted on a substrate. Theinspection method includes projecting grating pattern light onto thesubstrate in a plurality of directions N-times while changing thegrating pattern light and capturing N-number of images by a camera,generating visibility maps of the directions by using the N-number ofimages in each of the directions, acquiring shadow regions of themeasurement object from the visibility maps of the directions, andmerging the shadow regions of the plurality directions to generate ashadow map.

The inspection method may further include inspecting the measurementobject by acquiring at least one information of a size and a position ofthe device from the shadow map.

The visibility map (Vi(x,y)) may be a ratio of amplitude (Bi(x,y)) toaverage (Ai(x,y)) (or (Vi(x,y)=Bi(x,y)/Ai(x,y))) in intensity of imageat each pixel.

Inspecting the measurement object by acquiring at least one informationof a size and a position of the device from the shadow map may includecomparing the shadow map and the shape template corresponding to thedevice within a specific tolerance value.

Comparing the shadow map and the shape template may include comparingthe shadow map and the template while moving the shape template from aninitial position.

Comparing the shadow map and the shape template may include multiplyinga value of zero or one in the shadow template, which is allottedaccording to a coordinate of pixel with a value of zero or one in theshadow map, which is allotted according a coordinate of pixel of aregion where the shadow map overlaps with the shadow template to getresult values, and summing up the result values, determining a positionwhere the sum of the result values becomes maximum to be a preliminaryposition of the device by moving the shadow template, and confirming thedevice is the device corresponding to the shadow template when themaximum value is no less than a criterion.

Still another exemplary embodiment of the present invention discloses aninspection method. The inspection method includes projecting gratingpattern light onto the substrate in a plurality of directions N-timeswhile changing the grating pattern light and capturing N-number ofimages by a camera, generating visibility maps of the directions byusing the N-number of images in each of the directions (N is an integergreater than two), acquiring shadow regions of the directions from themeasurement object from the visibility maps of the directions,compensating the shadow regions of the directions, which are acquired,and merging the shadow regions of the directions, which are compensated,to generate a shadow map.

The visibility map (Vi(x,y)) may be a ratio of amplitude (Bi(x,y)) toaverage (Ai(x,y)) (or (Vi(x,y)=Bi(x,y)/Ai(x,y))) in intensity of imageat each pixel.

Compensating the shadow regions of the directions may be performed bymultiplying amplitude ((Bi(x,y)) with each pixels of the shadow regionof the directions, which is acquired.

Compensating the shadow regions of the directions may include setting upa pixel of a shadow regions of the directions to be a shadow when theamplitude ((Bi(x,y)) of the pixel is no greater than a criterion that ispreviously set up.

The inspection method may further include acquiring at least oneinformation of a size and a position of the measurement object from theshadow map.

According to the present invention, wanted device is extracted by usingthe contrast map on which height of the device is reflected and/or theshadow map of the device. Therefore, the method of the present inventionis less sensitive to the color of the device and illumination than theconventional method using two dimensional image (or picture), so thatthe device may be easily discriminated even when the dimension of thedevice is changed.

Additionally, the method of the present invention is not affected bynoise around the device, which is induced by patterns or silk screenpatterns formed around the device, or noise of the device, which isinduced by the camera. Even when other device, which may be confusedwith the device, is mounted, the device is compared with the template sothat the device may be clearly discriminated.

Furthermore, the method may clearly discriminate the device even whenthe fillet of the device is small, since the method does not uses thefillet but the contrast map in discriminating the device.

The shadow map is independent from measurement height range so thatinformation of the device 910, such as a position, a size, a rotationangle, etc., may be acquired regardless of the height of the device,even when the height of the device exceeds the measurement height rangeof the apparatus for measuring a three-dimensional shape.

Additionally, when the shadow regions of the directions acquired fromthe visibility map is compensated by the amplitude information, thenoise of the shadow region may be minimized to enhance inspectionreliability of the measurement object.

Furthermore, when the shadow regions are extracted using the amplitudemaps of the directions having less noise than the visibility maps of thedirections, a reliability of the shadow region may be enhanced.

Furthermore, a region of a measurement object may be exactly extractedusing the visibility map even when the height of the device exceeds themeasurement height range of the apparatus for measuring athree-dimensional shape.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention, andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a schematic view showing an apparatus for measuring athree-dimensional shape, which may be used for an inspection method fora three dimensional shape according to an exemplary embodiment of thepresent invention.

FIG. 2 is a flow chart showing a method for inspecting athree-dimensional shape according to exemplary embodiment of the presentinvention.

FIG. 3 is a schematic view showing an example of a shape template.

FIG. 4 is a flow chart showing a step of acquiring information of device(step S140) in FIG. 2 according to an exemplary embodiment of thepresent invention.

FIG. 5 is a conceptual view showing a method of comparing a targetdevice with a device corresponding to a shape template.

FIG. 6 is an image of a device, for example, when the device is a chip.

FIG. 7 is an image expressed by a contrast map of the chip in FIG. 6.

FIG. 8 is an image expressed by a contrast map of the chip in FIG. 6,when visibility information is reflected.

FIG. 9 is a flow chart showing a method for inspecting athree-dimensional shape according to another exemplary embodiment of thepresent invention.

FIG. 10 is a conceptual view showing an example of a shadow template.

FIG. 11 is a flow chart showing a step of generating a shadow map byusing visibility information (step S230) in FIG. 9 according to anotherexemplary embodiment of the present invention.

FIG. 12 is a flow chart showing a step of acquiring device information(step S240) in FIG. 9.

FIG. 13 is a conceptual view showing a method of comparing a targetdevice with a device corresponding to a shadow template.

FIG. 14 is a schematic view showing an apparatus for measuring athree-dimensional shape, which may be used for a method for inspecting ameasurement object according to an exemplary embodiment of the presentinvention.

FIG. 15 is a plan view showing a portion of a substrate, on which ameasurement object is mounted.

FIG. 16 is a flow chart showing a method for inspecting a measurementobject according to still another exemplary embodiment of the presentinvention.

FIG. 17 is a figure showing visibility maps of a plurality ofdirections.

FIG. 18 is a figure showing amplitude maps of a plurality of directions.

FIG. 19 is a figure showing compensation maps of a plurality ofdirections, in which shadow regions of a plurality of directions arecompensated.

FIG. 20 is a figure showing a shadow map in which compensated shadowregions of a plurality of directions are merged.

FIG. 21 is a flow chart showing a method for inspecting a measurementobject according to still another exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The invention is described more fully hereinafter with reference to theaccompanying drawings, in which embodiments of the invention are shown.This invention may, however, be embodied in many different forms andshould not be construed as limited to the embodiments set forth herein.Rather, these embodiments are provided so that this disclosure isthorough, and will fully convey the scope of the invention to thoseskilled in the art. In the drawings, the size and relative sizes oflayers and regions may be exaggerated for clarity. Like referencenumerals in the drawings denote like elements.

It will be understood that when an element or layer is referred to asbeing “on” or “connected to” another element or layer, it can bedirectly on or directly connected to the other element or layer, orintervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on” or “directly connected to”another element or layer, there are no intervening elements or layerspresent.

FIG. 1 is a schematic view showing an apparatus for measuring athree-dimensional shape, which may be used for an inspection method fora three dimensional shape according to an exemplary embodiment of thepresent invention.

Referring to FIG. 1, an apparatus for measuring a three-dimensionalshape, which may be used for an inspection method for a threedimensional shape according to an exemplary embodiment of the presentinvention, includes a stage section 100, an image capturing section 200,first and second projecting sections 300 and 400, an image storingsection 500, a module control section 600 and a central control section700.

The stage section 100 may include a stage 110 and a stage transferringunit 120. The stage 110 supports the substrate 10 on which themeasurement object 10 is mounted.

The stage transferring unit 120 transfers the stage 110. In the presentembodiment, the stage 110 transfers the substrate 10 with respect to theimage capturing section 200 and the first and second projecting sections300 and 400, so that a measuring position of the substrate 10 may bechanged.

The image capturing section 200 is disposed over the stage 110. Theimage capturing section 200 receives light reflected on the measurementobject 10 to capture an image of the measurement object 10. That is, theimage capturing section 200 receives light projected by the first andsecond projecting sections 300 and 400 and reflected on the measurementobject 10 to capture the image of the measurement object 10 formeasuring a three-dimensional shape.

The image capturing section 200 may include a camera 210, an imaginglens 220, a filter 230 and a lamp 240. The camera 210 receives lightreflected on the measurement object 10 to capture the image of themeasurement object 10. For example, a CCD camera or a CMOS camera may beemployed as the camera 210. The imaging lens 220 is disposed under thecamera 210 to make an image of the measurement object 10 onto the camera210. The filter 230 is disposed under the imaging lens 220 to filterlight reflected by the target object 10 to provide filtered light to theimaging lens 220. For example, the filter 230 may include at least oneof a frequency filter, a color filter and intensity a control filter.The lamp 240 is disposed under the filter 230, for example in a circularshape. The lamp 240 may irradiate light onto the measurement object 10to make an image for a specific purpose such as a two dimensional shapeof the measurement object 10.

The first projecting section 300 may be disposed at a first side of theimage capturing section 200 such that the first projecting section 300projects light slantly with respect to the stage 110. The firstprojecting section 300 may include a first projecting unit 310, a firstgrating unit 320, a first grating transfer unit 330 and a first focusinglens 340. The first projecting unit 310 may include a light sourcegenerating light and at least one lens. The first grating unit 320 isdisposed under the first projecting unit 310 to convert the lightgenerated by the first projecting unit 310 into a first grating patternlight. The first grating transfer unit 330 is connected to the firstgrating unit 320 to transfer the first grating unit 320. For example, aPZT piezoelectric transfer unit or a precise linear transfer unit may beemployed as the first grating transfer unit 330. The first focusing lens340 is disposed under the first grating unit 320 to focus the firstgrating pattern light generated by the first grating unit 320 onto themeasurement object 10.

The second projecting section 400 may be disposed at a second side ofthe image capturing section 200, which is opposite to the first side,such that the second projecting section 400 projects light slantly withrespect to the stage 110. The second projecting section 400 may includea second projecting unit 410, a second grating unit 420, a secondgrating transfer unit 430 and a second focusing lens 440. The secondprojecting section 400 is substantially the same as the first projectingsection 300 explained above. Therefore, any further explanation will beomitted.

When the first projecting section 300 projects N-number of first gratingpattern lights toward the measurement object 10 while the first gratingunit 320 is transferred by the first grating transfer unit 330, theimage capturing section 200 receives N-number of first grating patternlights reflected by the measurement object 10 to capture the N-number offirst grating pattern lights reflected by the measurement object 10.Likewise, the second projecting section 400 projects N-number of secondgrating pattern lights toward the measurement object 10 while the secondgrating unit 420 is transferred by the second grating transfer unit 430,the image capturing section 200 receives N-number of second gratingpattern lights reflected by the measurement object 10 to capture theN-number of second grating pattern lights reflected by the measurementobject 10. For example, the integer number N is three or four.

In the present embodiment, only the first and second projecting sections300 and 400 project the first and second grating pattern lights,respectively. However, the number of the projecting section may be morethan two. That is, the grating pattern lights may be irradiated towardthe target object 10 in various directions to capture various kinds ofpattern images. For example, when three projecting sections are disposedat apexes of an equilateral triangle, respectively, three kinds ofgrating pattern lights may be projected onto the measurement object 10.In this case, the image capturing section 200 is disposed at a center ofthe equilateral triangle. For example, when four projecting sections aredisposed at apexes of a square, respectively, four kinds of gratingpattern lights may be projected onto the measurement object 10. In thiscase, the image capturing section 200 is disposed at a center of thesquare.

The image storing section 500 is electrically connected with the camera210 of the image capturing section 200 and receives the pattern imagesfrom the camera 210 to store the pattern images. For example, the imagestoring section 500 includes an image system receiving the N-number offirst pattern images and the N-number of second pattern images from thecamera 210 to store the N-number of first pattern images and theN-number of second pattern images.

The module control section 600 is electrically connected to the stagesection 100, the image capturing section 200, the first projectingsection 300 and the second projecting section 400 to control them. Themodule control section 600 includes, for example, a Z-axis controller,an illumination controller, a grating controller and a stage controller.The Z-axis controller may transfer the image capturing section 200, thefirst projecting section 300 and the second projecting section 400 alonga Z-axis direction for focusing. The illumination controller controlsthe first and second projecting units 310 and 410, respectively togenerate light. The grating controller controls the first and secondgrating transfer units 330 and 430 to transfer the first and secondgrating units 320 and 420, respectively. The stage controller controlsthe stage transferring unit 120 to transfer the stage 110 along anX-axis and a Y-axis direction.

The central control section 700 is electrically connected to the imagestoring section 500 and the module control section 600 to control theimage storing section 500 and the module control section 600. In detail,the central control section 700 receives the N-number of first patternimages and the N-number of second pattern images from the image systemof the image storing section 500 to acquire 3D image data of theelectronic device 20 by using N-bucket algorithm. The 3D image dataincludes height information corresponding to points of the substrate 10.Furthermore, the central control section 700 may control the Z-axiscontroller, the illumination controller, the grating controller and thestage controller of the module control section 600. In order forperforming above operation, the central control section 700 may include,for example, an image processing board, a control board and an interfaceboard.

Hereinafter, a method for inspecting a device mounted on a printedcircuit board by using an apparatus for measuring a three-dimensionalshape, which is described above, will be explained.

FIG. 2 is a flow chart showing a method for inspecting athree-dimensional shape according to exemplary embodiment of the presentinvention, and FIG. 3 is a schematic view showing an example of a shapetemplate.

Referring to FIG. 2 and FIG. 3, in order to inspect a device mounted ona printed circuit board, a shape template 800, in which the shape of thedevice is abstracted, is generated (step S110). The abstracted device810 may includes a chip having, for example, a hexahedron shape.

For example, in abstracting the device 810, the shape template 800 maybe set up in advance such that a first region corresponding to thedevice 810 may be expressed in white color and a second region notcorresponding to the device 810 may be expressed in black color as shownin FIG. 3. In FIG. 3, a hatched region corresponds to the device 810. Inthis case, the shape template 800 is generated in a digital image, andthe first region may be set to be one and the second region may be setto be zero.

The shape template 800 may be defined by a template determinant. Thatis, the template determinant may determine the shape template 800. Forexample, when the device 810 is a chip with a hexahedron shape, thetemplate determinant may include a planar area of the chip. In detail,the template determinant may include a width X of the chip and a lengthY of the chip, and the shape template 800 may be defined by the templatedeterminant having the width and the length of the chip.

Then, height information is acquired by pixels of the measurement targetby projecting grating pattern light onto the measurement target in atleast two directions (step S120).

The height information acquired by pixels of the measurement target maybe calculated from data obtained by measuring the measurement target,for example, by using the apparatus for measuring a three-dimensionalshape in FIG. 1.

Then, a contrast map, in which a contrast corresponding to the heightinformation is set up by pixels, is generated (step S130). Pixels of acomparison target device (Hereinafter, referred to as “target device”)mounted on the measurement target may be set up to have greater contrastvalue when a height of the pixels becomes greater in the heightinformation. Therefore, the contrast map is generated such that a regionwhere the target device is positioned is brighter than a region wherethe target device is not positioned.

In this case, the contrast map is generated according to the heightinformation. Therefore, the contrast map is independent from a color ofthe target device, or a character or a figure printed on the targetdevice. Furthermore, the contrast map is independent from a color, acharacter or a figure of environment of the target device. That is, thecontrast map represents only gray scale of the target device accordingto height of the target device. Therefore, the shape of the targetdevice may be extracted more exactly in comparison with a conventionaltwo dimensional image.

On the other hand, in order to extract the shape of the target devicemore exactly, visibility information of the measurement target may beacquired by pixel to be used.

The visibility is a ratio of amplitude Bi(x,y) to average Ai(x,y). Ingeneral, the visibility increases when reflectivity increases. Thevisibility Vi(x,y) may be expressed as follows,Vi(x,y)=Bi(x,y)/Ai(x,y).

The grating pattern light may be projected onto the printed circuitboard in various directions to acquire various kinds of pattern images.As shown in FIG. 1, the image storing section 500 extracts N-number ofintensity signals I^(i) ₁, I^(i) ₂, . . . , I^(i) _(N) at a positioni(x,y) in X-Y plane from N-number of pattern images captured by thecamera 210, and the average Ai(x,y) and the visibility Vi(x,y) arecalculated by using N-bucket algorithm.

For example, the visibility may be expressed as follows in case that N=3and N=4, respectively.

In case that N=3,

${{A_{i}\left( {x,y} \right)} = \frac{I_{1}^{i} + I_{2}^{i} + I_{3}^{i}}{3}},{{V_{i}\left( {x,y} \right)} = {\frac{B_{i}}{A_{i}} = {\frac{\sqrt{\left( {{2I_{1}^{i}} - I_{2}^{i} - I_{3}^{i}} \right)^{2} + {3\left( {I_{2}^{i} - I_{3}^{i}} \right)^{2}}}}{\left( {I_{1}^{i} + I_{2}^{i} + I_{3}^{i}}\; \right)}.}}}$

In case that N=4,

${{A_{i}\left( {x,y} \right)} = \frac{I_{1\;}^{i} + I_{2}^{i} + I_{3}^{i} + I_{4}^{i}}{4}},{{V_{i}\;\left( {x,y} \right)} = {\frac{B_{i}}{A_{i}} = {\frac{2\sqrt{\left( {I_{1}^{i} - I_{3}^{i}} \right)^{2} + \left( {I_{2}^{i} - I_{4}^{i}} \right)^{2}}}{\left( {I_{1}^{i} + I_{2}^{i} + I_{3}^{i} + I_{4}^{i}} \right)}.}}}$

The visibility information may be acquired by projecting grating patternlights onto the measurement target in at least two directions, likewisea step of acquiring height information by pixels of the measurementtarget (step S120). That is, the visibility information by pixels may beeasily acquired also from data of the target obtained by using, forexample, the apparatus for measuring a three-dimensional shape in FIG.1.

The contrast by pixels may be defined by a value obtained by multiplyingthe height information with the visibility information above. Ingeneral, when the reflectivity of a device is higher than environment,the visibility of the device is much greater than the visibility of theenvironment. Therefore, when the visibility information is reflected onthe contrast map, the device may be emphasized in comparison with thecontrast map on which only the height information is reflected.

Referring again to FIG. 2, then, information of the device 810, whichcorresponds to the shape template 800 in the measurement target, isacquired by comparing the contrast map of the measurement target withthe shape template 800 (step S140). The information of the device 810may include existence, a real size and a disposition status of thedevice 810, etc.

FIG. 4 is a flow chart showing a step of acquiring information of device(step S140) in FIG. 2 according to an exemplary embodiment of thepresent invention.

Referring to FIG. 4, in order to acquire the information of the device810, which corresponds to the shape template 800 in the measurementtarget, existence of the device 810 corresponding to the shape template800 is firstly checked in the measurement target (step S142).

For example, an inspection area (or region of interest) is set up andthe existence of the target device in the inspection area is checked. Inthis case, the inspection area may be set up, for example, by using CADinformation in which the shape of the measurement target is recorded.The CAD information includes design information of the measurementtarget. Alternatively, the inspection area may be set up by usingstudied information obtained in a studying mode. In the studying mode, abare board of a printed circuit board is studied to get design standardinformation of the printed circuit board, and the studied informationobtained in the studying mode may be used in setting up the inspectionarea.

FIG. 5 is a conceptual view showing a method of comparing a targetdevice with a device corresponding to a shape template.

Referring to FIG. 5, in order to check if the target device 820 is thedevice 810 corresponding to the shape template 800, the inspection areaROI is set up first in the printed circuit board, and then the shapetemplate 800 is compared with the contrast map while moving the shapetemplate 800 from an initial position 800 a in sequence.

In order to compare the shape template 800 with the contrast map, thevalue of zero or one in the shape template 800, which is allottedaccording to a coordinate of pixel, is multiplied by a contrast value ofa region where the contrast map overlaps with the shape template 800 toget result values, and the result values are summed. Then, a positionwhere the sum of the result values is maximum, is determined to be apreliminary position of the device 810. When the maximum sum of theresult values is equal to or greater than a criterion, the target device820 is determined to be the device 810 corresponding to the shapetemplate 800.

The device 810 corresponding to the shape template 800 has a certainsize. The target device 820 of the measurement target may have differentsize, and the target device 820 may be rotated. Therefore, a tolerancevalue may be provided in determining the device 810 recorded in theshape template 800 to be the target device 820, and the contrast map andthe shape template 800 may be compared with each other in the tolerancevalue of the template determinant. For example, the tolerance value maybe about 50% to about 150% of the device 810 corresponding to the shapetemplate 800 in size. Additionally, an angle tolerance may be providedin determining the device 810 corresponding to the shape template 800 tobe the target device 820, and the contrast map may be compared with theshape template 800 while rotating one of them.

Referring again to FIG. 4, then, when the device 810 exists in themeasurement target, the information of size, position and rotation angleof the device (or the target device 820) may be acquired (step S144).The above information may be easily acquired through the contrast map.

After acquiring information of the device corresponding to the shapetemplate 800 in the measurement target (step S140), the information ofthe device 810 may be used in various ways for a method for inspectingthree dimensional shape.

For example, the device corresponding to the shape template 800 may bechecked if the device is inferior one by using the information of thedevice (step S150). That is, the device may be checked if the device isinferior one by confirming that the device is properly disposed on themeasurement target by using the size information, rotation information,etc. Additionally, information of other device or element may beobtained by eliminating the information of the device from themeasurement target.

On the other hand, a portion of information of the device may be removedin the information of the device, and a remaining portion of informationmay be used for checking if the device is inferior one.

For example, when the device is a chip mounted on a printed circuitboard, information of a terminal of a chip, in which information of abody of the chip is removed, or information of pad electricallyconnected to the terminal may be acquired without noise. Therefore,using the information above, the inferior one of the device may bechecked.

As an exemplary embodiment, when the device is a chip mounted on aprinted circuit board, a chip body of the chip is extracted first, chipbody information regarding the chip body is removed from chipinformation regarding the chip, and then the chip mounted on the printedcircuit board may be checked if the chip is inferior one by using thechip information in which the chip body information is removed. That is,a condition of connection between the terminal of the chip and the padmay be checked.

Hereinafter, the conventional two dimensional image (or picture) and thecontrast map, on which height information (which corresponds to threedimensional information) is reflected, are compared referring tofigures.

FIG. 6 is an image of a device, for example, when the device is a chip.

Referring to FIG. 6, a shape of a chip body in the image may beestimated to be a rectangle. However, a contour of the chip body cannotbe clearly defined. Especially, it is not easy to find what regioncorresponds to chip body, and what region corresponds to a solder, a padand a terminal.

Furthermore, the image is a two dimensional image (or a picture), sothat number printed on the chip body and a portion with different colorare displayed in the image.

FIG. 7 is an image expressed by a contrast map of the chip in FIG. 6.

Referring to FIG. 7, a shape of a chip body in the image may be clearlyshown to be a rectangle. The image in FIG. 7 is an image on which threedimensional information such as height information by pixel isreflected. In detail, the image in FIG. 7 is expressed to have abrighter contrast region in accordance with height. Therefore, the chipbody with the same height is brightly expressed and the solder, the pad,the terminal, etc. which are lower than the chip body is darklyexpressed, so that the chip body may be easily discriminated.

Furthermore, the height information is reflected on the image so thatthe color of the chip body, a number and a character printed on the chipbody, etc., are not expressed in the image. Therefore, the color of thechip body and the number or the character printed on the chip body donot disturb in discriminating the chip body. Especially, even when thechip body has a complex color and complex character printed thereon, theshape of the chip body may be easily acquired by using the contrast map.

FIG. 8 is an image expressed by a contrast map of the chip in FIG. 6,when visibility information is reflected.

Referring to FIG. 8, the shape of the chip body may be more clearlydiscriminated in FIG. 8. The image in FIG. 8 is the contrast map onwhich the visibility information is reflected, so that the chip body isemphasized to be more bright and other portions are expressed to be moredark. As a result, the chip body is emphasized, so that the shape of thechip body may be easily acquired.

As described above, according to the present embodiment, the device maybe extracted by using the contrast map on which height information isreflected. Therefore, the method of the present invention is lesssensitive to the color of the device and illumination than theconventional method using two dimensional image (or picture), so thatthe device may be easily discriminated even when the dimension of thedevice is changed.

Additionally, the method of the present invention is not affected bynoise around the device, which is induced by patterns or silk screenpatterns formed around the device, or noise of the device, which isinduced by the camera. Even when other device, which may be confusedwith the device, is mounted, the device is compared with the template sothat the device may be clearly discriminated.

Furthermore, the method may clearly discriminate the device even whenthe fillet of the device is small, since the method does not uses thefillet but the contrast map in discriminating the device.

FIG. 9 is a flow chart showing a method for inspecting athree-dimensional shape according to another exemplary embodiment of thepresent invention, and FIG. 10 is a conceptual view showing an exampleof a shadow template.

Referring to FIG. 9 and FIG. 10, in order to inspect a device mounted ona printed circuit board, a shadow template 900, in which the shadow ofthe device is abstracted, is generated (step S210). The abstracteddevice 910 may includes a chip having, for example, a hexahedron shape.

For example, in abstracting the shadow of the device 910, which isgenerated when light is slantly irradiated onto the device, the shadowtemplate 900 may be set up in advance such that a first regioncorresponding to the shadow of the device 910 may be expressed in whitecolor and a second region not corresponding to the shadow of the device910 may be expressed in black color as shown in FIG. 10. In FIG. 10, ahatched region corresponds to the shadow of the device 910. In thiscase, the shadow template 900 is generated in a digital image, and thefirst region may be set to correspond to one and the second region maybe set to correspond to zero.

The shadow template 900 may be defined by a template determinant. Thatis, the template determinant may determine the shadow template 900. Forexample, when the device 910 is a chip with a hexahedron shape, thetemplate determinant may include a dimension of the chip and aprojecting angle of grating pattern image light. In detail, the templatedeterminant may include a width X of the chip, a length Y of the chipand a height (not shown) of the chip corresponding to the dimension ofthe chip, and the shadow template 900 may be defined by the templatedeterminant having the width, the length and the height of the chip.

Then, shadow information is acquired by pixels of the measurement targetby projecting grating pattern light onto the measurement target in aplurality of directions (step S220).

The shadow information acquired by pixels of the measurement target maybe calculated from data obtained by measuring the measurement target,for example, by using the apparatus for measuring a three-dimensionalshape in FIG. 1.

Then, a shadow map, in which shadow information obtained in variousdirections are merged, is generated (step S230). For example, accordingto apparatus for measuring a three-dimensional shape, which measures acomparison target device (Hereinafter, referred to as “target device”)in four directions by slantly projecting the target device, shadows ofthe target device is generated in four directions, and the shadows infour directions are merged to generate the shadows map surrounding thetarget device. For example, the shadow map may be formed such that oneis assigned when there is a shadow and zero is assigned when there isnot a shadow according to a pixel coordinate.

The shadow map is independent from measurement height range so thatinformation of the device 910, such as a position, a size, a rotationangle, etc., may be acquired regardless of the height of the device,even when the height of the device exceeds the measurement height rangeof the apparatus for measuring a three-dimensional shape.

In this case, the shadow map is generated according to the shadowinformation. Therefore, the shadow map is independent from a color ofthe target device, or a character or a figure printed on the targetdevice. Furthermore, the shadow map is independent from a color, acharacter or a figure of environment of the target device. That is, theshadow map represents only gray scale of the target device according toexistence of the shadow of the target device. Therefore, the shape ofthe target device may be extracted more exactly in comparison with aconventional two dimensional image.

On the other hand, in order to extract the shape of the target devicemore exactly, visibility information of the measurement target may beacquired by pixel to be used as described referring to FIG. 2 and FIG.3.

The visibility information may be acquired by projecting grating patternlights onto the measurement target in a plurality of directions,likewise a step of acquiring shadow information by pixels of themeasurement target (step S220). That is, the visibility information bypixels may be easily acquired also from data of the target obtained byusing, for example, the apparatus for measuring a three-dimensionalshape in FIG. 1.

FIG. 11 is a flow chart showing a step of generating a shadow map byusing visibility information (step S230) in FIG. 9 according to anotherexemplary embodiment of the present invention.

Referring to FIG. 11, in order to generate the shadow map, a preliminaryshadow map is generated first according to the shadow information byeach pixel (step S232). Then, the device portion is removed from thepreliminary shadow map by using the visibility information (step S234).Then, the shadow map in which the device portion is removed is finalized(step S236).

In general, when the reflectivity of a device is higher thanenvironment, the visibility of the device is much greater than thevisibility of the environment. Therefore, when the visibilityinformation is reflected on the shadow map, the shadow may be clearlydiscriminated even when the device has a black color that is similar toa color of the shadow.

Referring again to FIG. 9, then, information of the device 910, whichcorresponds to the shadow template 900 in the measurement target, isacquired by comparing the shadow map of the measurement target with theshadow template 900 (step S240). The information of the device 910 mayinclude existence, a real size and a disposition status of the device910, etc.

FIG. 12 is a flow chart showing a step of acquiring device information(step S240) in FIG. 9.

Referring to FIG. 9 and FIG. 12, in order to acquire the information ofthe device 910, which corresponds to the shadow template 900 in themeasurement target, existence of the device 910 corresponding to theshadow template 900 may be firstly checked in the measurement target(step S242).

For example, an inspection area (or region of interest) is set up andthe existence of the target device in the inspection area is checked. Inthis case, the inspection area may be set up, by the same methoddescribed referring to FIG. 4.

FIG. 13 is a conceptual view showing a method of comparing a targetdevice with a device corresponding to a shadow template.

Referring to FIG. 13, in order to check if the target device 920 is thedevice 910 corresponding to the shadow template 900, the inspection areaROI may be set up first in the printed circuit board, and then theshadow template 900 may be compared with the shadow map while moving theshadow template 900 from an initial position 900 a in sequence.

In order to compare the shadow template 900 with the shadow map, thevalue of zero or one in the shadow template 900, which is allottedaccording to a coordinate of pixel, is multiplied by the value of zeroor one in the shadow map, which is allotted according to the coordinateof the pixel to get result values, and the result values are summed. Inthis case, when a region where the hatched region of the shadow template900 in FIG. 13 overlaps with the hatched region of the shadow mapincreases in size, the result value becomes greater. Then, a positionwhere the sum of the result values is maximum, is determined to be apreliminary position of the device 910. When the region where thehatched region of the shadow template 900 in FIG. 13 overlaps with thehatched region of the shadow map is maximum in size, the result valuebecomes maximum and the shadow template 900 and the shadow map aresubstantially coincide with each other. Then, when the maximum sum ofthe result values is equal to or greater than a criterion, the targetdevice 920 is determined to be the device 910 corresponding to theshadow template 900. For example, the criterion may be set to a numberobtained by multiplying the number one in the shadow template 900 with aspecific value.

The device 910 corresponding to the shadow template 900 has a certainsize. The target device 920 of the measurement target may have differentsize, and the target device 920 may be rotated. Therefore, a tolerancevalue may be provided in determining the device 910 recorded in theshadow template 900 to be the target device 920, and the shadow map andthe shadow template 900 may be compared with each other in the tolerancevalue of the template determinant. For example, the tolerance value maybe about 50% to about 150% of the device 910 corresponding to the shadowtemplate 900 in a horizontal length X, a vertical length Y and a widthW. In this case, the width W may be substantially the same in alldirection, but may be different according to directions. Additionally,an angle tolerance may be provided in determining the device 910corresponding to the shadow template 900 to be the target device 920,and the shadow map may be compared with the shadow template 900 whilerotating one of them.

Referring again to FIG. 12, then, when the device 910 exists in themeasurement target, the information of size, position and rotation angleof the device (or the target device 920) may be acquired (step S244).The above information may be easily acquired through the shadow map.

After acquiring information of the device corresponding to the shadowtemplate 900 in the measurement target (step S240), the information ofthe device 910 may be used in various ways for a method for inspectingthree dimensional shape.

For example, the device corresponding to the shadow template 900 may bechecked if the device is inferior one by using the information of thedevice (step S250).

The step S250 is substantially the same as the step of S150 in FIG. 2,thus any further explanation will be omitted.

As described above, according to the present embodiment, the device maybe extracted by using the shadow map on which shadow information isreflected. Therefore, the method of the present invention is lesssensitive to the color of the device and illumination than theconventional method using two dimensional image (or picture), so thatthe device may be easily discriminated even when the dimension of thedevice is changed.

Additionally, the method of the present invention is not affected bynoise around the device, which is induced by patterns or silk screenpatterns formed around the device, or noise of the device, which isinduced by the camera. Even when other device, which may be confusedwith the device, is mounted, the device is compared with the template sothat the device may be clearly discriminated.

Furthermore, the shadow is independent from measurement height range sothat information of the device, such as a position, a size, a rotationangle, etc., may be acquired regardless of the height of the device,even when the height of the device exceeds the measurement height rangeof the apparatus for measuring a three-dimensional shape.

FIG. 14 is a schematic view showing an apparatus for measuring athree-dimensional shape, which may be used for an inspection method fora three dimensional shape according to an exemplary embodiment of thepresent invention.

Referring to FIG. 14, an apparatus for measuring a three-dimensionalshape according to an exemplary embodiment of the present inventionincludes a stage 1140, at least one projecting section 1110 and a camera1130. The state 1140 supports and transfers a substrate 1150 on which ameasurement object is formed. The at least one projecting section 1110projects grating pattern light onto the substrate 1150. The camera 1130captures an image of the substrate 1150. The apparatus for measuring athree-dimensional shape may further include an illuminating section 1120for irradiating light onto substrate 1150, separated from the projectingsection 1110. The illuminating section 1120 is disposed adjacent to thestage 1140.

The projecting section 1110 is used for measuring three dimensionalshape of the measurement object on the substrate 1150. In order forthat, the projecting section 1110 slantly projects grating pattern lightonto the substrate 1150. For example, the projecting section 1110includes a light source 1112, a grating unit 1114, a grating transferunit 1116 and a focusing lens 1118. The light source 1112 generateslight. The grating unit 1114 converts light generated by the lightsource 1112 into grating pattern light. The grating transfer unit 1116transfers the grating unit 1114 by a specific distance. The focusinglens 1118 focuses the grating pattern light converted by the gratingunit 1114 onto the measurement object. The grating unit 1114 may betransferred by 2π/N (N is an integer number) for phase shifting by thegrating transfer unit 1116 such as a piezo actuator (PZT). Theprojecting section 1110 having the above elements projects gratingpattern light toward the substrate 1150 at times when the grating unit1114 is transferred by the grating transfer unit 1116, step by step andthe camera 1130 captures an image of the substrate 1150 when theprojecting section 1110 projects the grating pattern light.

In order to improve measurement accuracy, a plurality of the projectingsections 1110 may be disposed along a circumference of a circle with thecamera 1130 disposed at a center thereof by a specific angle. Forexample, four projecting sections 1110 may be disposed at thecircumference of a circle by ninety degrees with respect to the camera1130, or eight projecting sections 1110 may be disposed at thecircumference of a circle by forty five degrees with respect to thecamera 1130.

The illuminating section 1120 has a circular shape, and may be disposedadjacent to the stage 1140. The illuminating section 1120 irradiateslight toward the substrate 1150 for checking an initial alignment orsetting up an inspection area. For example, the illuminating section1120 may include a fluorescent lamp emitting white light. Alternatively,the illuminating section 1120 may include a red LED emitting red light,a green LED emitting green light and a blue LED emitting blue light.

The camera 1130 is disposed over the stage 1140, and receives lightreflected by the substrate 1150 to capture an image of the substrate1150. For example, the camera 1130 captures a grating pattern imagereflected by the substrate 1150 when the projecting section 1110projects grating pattern light onto the substrate 1150, and an image ofthe substrate 1150 when illuminating section 1120 irradiates light ontothe substrate 1150. The camera 1130 may include a CCD camera or a CMOScamera for capturing an image.

The apparatus for measuring a three-dimensional shape, which has aboveexplained structure, emits grating pattern light or light by using theprojecting section 1110 or the illuminating section 1120 onto thesubstrate 1150, and captures the grating pattern image or the imagereflected by the substrate 1150 by using the camera 1130 to measurethree-dimensional image or two dimensional image, respectively. Theapparatus for measuring a three-dimensional shape in FIG. 14 is only anexample, and various modifications of the apparatus for measuring athree-dimensional shape may be possible.

Hereinafter, a method for inspecting a device mounted on a printedcircuit board by using the apparatus for measuring a three-dimensionalshape, which is described above, will be explained.

FIG. 15 is a plan view showing a portion of a substrate, on which ameasurement object is mounted, FIG. 16 is a flow chart showing a methodfor inspecting a measurement object according to still another exemplaryembodiment of the present invention, FIG. 17 is a figure showingvisibility maps of a plurality of directions, FIG. 18 is a figureshowing amplitude maps of a plurality of directions, FIG. 19 is a figureshowing compensation maps of a plurality of directions, in which shadowregions of a plurality of directions are compensated, and FIG. 20 is afigure showing a shadow map in which compensated shadow regions of aplurality of directions are merged.

Referring to FIG. 14, FIG. 15 and FIG. 16, in order to inspect themounting status of a measurement object 1152 such as an electronicdevice on a substrate 1150, grating pattern light is projected onto thesubstrate 1150, on which the measurement object 1152 is mounted, N-timesin a plurality of directions, respectively and images of the substrate1150 are captured by the camera 1130 (step S1110). Here, N is an integergreater than two. Then, visibility maps of the directions are generatedusing N-number of images captured by the camera 1130 in the plurality ofdirections (step S1120).

In detail, when a plurality of projecting sections 1110 projects gratingpattern light onto the substrate 1150 in sequence, the camera 1130captures images in sequence to generate the visibility maps of thedirections. In this case, the apparatus for measuring athree-dimensional shape may acquire images of the directions through amulti-channel phase shift moire method. For example, each of theprojecting sections 1110 projects grating pattern light onto thesubstrate 1150 while shifting the grating pattern light several times,and the camera 1130 captures phase shifted images of the substrate 1150to generate the visibility maps of the directions from the phase shiftedimages. On the other hand, amplitude maps of the directions may begenerated from the phase shifted images.

The visibility map may be generated by using amplitude Bi(x,y) andaverage Ai(x,y) of intensity of captured image. The visibility is thesame as described referring to FIG. 2 and FIG. 3. Thus, any furtherexplanation will be omitted.

The apparatus for measuring a three-dimensional shape may generatevisibility maps of a plurality of directions in FIG. 17 and amplitudemaps of a plurality of directions in FIG. 18 by using the visibilityinformation and the amplitude information.

Referring to FIG. 19, when the visibility maps of a plurality ofdirections are generated, shadow regions 1154 of four directions, whichregards to the measurement object 1152, is acquired from the visibilitymaps of a plurality of directions (step S1130). The measurement object1152 mounted on the substrate 1150 has a certain height. Therefore, whenthe projecting section 1110 projects grating pattern light toward themeasurement object 1152, a shadow region 1154 is generated at a sidethat is opposite to the projecting section 1110 with respect to themeasurement object 1152. For example, the shadow region 1154 isrelatively dark in comparison with other regions, so that the shadowregion 1154 is displayed in black in visibility maps of the directionsand amplitude maps of the directions.

Then, the shadow regions 1154 of the directions, which are acquiredthrough the above process, are compensated (step S1140). The visibility(Vi(x,y)) may be a large number in a region where the average (Ai(x,y))is very small, for example, (0.xxx) even through the amplitude Bi(x,y)is small, so that a noise region 1156 where a real shadow region 1154 isbrightly displayed as shown in FIG. 17 may be generated. Therefore, inorder to remove the noise region 1156, shadow regions 1154 of thedirections are compensated. According to one exemplary embodiment forcompensating the shadow regions 1154 of the directions, the each pixelof the shadow regions 1154 of the directions is multiplied by theamplitude Bi(x,y). According to another exemplary embodiment forcompensating the shadow regions 1154 of the directions, a pixel of theshadow regions 1154 of the directions is set up to be a shadow when theamplitude Bi(x,y) of the pixel is no greater than a criterion that ispreviously set up.

By compensating the shadow regions 1154 of the directions through theabove described method, most of the noise regions 1156 of the shadowregions 1154 of the directions may be removed, so that more reliableshadow regions 1154 of the directions may be acquired. Additionally, aregion of a measurement object may be exactly extracted using thevisibility map even when the height of the device exceeds themeasurement height range of the apparatus for measuring athree-dimensional shape.

When the shadow regions 1154 of the directions are compensated, thecompensated shadow regions 1154 of the directions, which arecompensated, are merged to generate a shadow map as shown in FIG. 20(step S1150). A real measurement object 1152 and the shadow region 1154neighboring the measurement object 1152 have relatively greater grayscale difference on the shadow map. Therefore, region of the measurementobject 1152 may easily set up. For example, the measurement object 1152may be displayed in a bright color and the shadow region 1154 may bedisplayed in a dark color in the shadow map. On the contrary, themeasurement object 1152 may be displayed in a dark color and the shadowregion 1154 may be displayed in a bright color in the shadow map.

Compensating the shadow regions may be performed after acquiring theshadow regions of the directions from the visibility maps of thedirections (step S1130). Alternatively, a merged shadow region may becompensated in the shadow map after the shadow regions of the directionsare merged to generate the shadow map (step S1150).

Then, a mounting status of the measurement object 1152 may be checked byusing the shadow map. In detail, information of a size, a position and arotation of the measurement object 1152 are acquired from the shadowmap, and mounting status of the measurement object 1152 may be checkedusing at least one of the information. For example, CAD data, in whichbasic information of the substrate is contained, includes information ofa size, a position and a rotation of the measurement object 1152.Therefore, mounting status of the measurement object 1152 may be checkedby comparing the information of the CAD data with the information of theshadow map.

Additionally, a step for generating a template for confirming themeasurement object 1152 by being compared with the shadow map may beadded. The template may be generated through the information of themeasurement object 1152 or through measuring performed by measuringapparatus, and the template may be stored to be used. In comparing theshadow map with the template, when a difference between the shadow mapand the template is within a tolerance, the measurement object isconfirmed. In this case, the tolerance may be set up by a user.

In the present embodiment, grating pattern lights are projected of aplurality of directions or four projecting sections 1110 are used.However, the number of direction in which the grating pattern light isprojected is not limited to four but may be variable.

FIG. 21 is a flow chart showing a method for inspecting a measurementobject according to still another exemplary embodiment of the presentinvention.

Referring to FIG. 21, in order to inspect mounting status of themeasurement object 1152, grating pattern lights are projected onto thesubstrate 1150, on which the measurement object 1152 is mounted, in aplurality of directions to acquire amplitude maps of the directions asshown in FIG. 18 (step S1210). The method of acquiring the amplitudemaps of a plurality of directions is previously described. Thus, anyfurther explanations will be omitted.

Then, regions in the amplitude maps of a plurality of directions, inwhich amplitude is no greater than a criterion which is previously setup, are determined to a shadow region, and shadow regions 1154 of thedirections are extracted (step S1220). In general, the shadow region hasrelatively lower amplitude than other region. Therefore, a region havinglower amplitude than a criterion may be considered as the shadow region.As described above, when the shadow regions are extracted using theamplitude maps of the directions having less noise than the visibilitymaps of the directions, a reliability of the shadow region may beenhanced.

Then, the shadow regions 1154 of the directions are merged to generate ashadow map (step S1230). The shadow map is previously explainedreferring to FIG. 20. Thus, any further explanation will be omitted.Furthermore, in the present embodiment, a step of inspecting of mountingstatus of the measurement object using the shadow map and a step ofgenerating template may be included.

On the other hand, in generating the shadow map, instead of using thevisibility maps of the directions or the amplitude maps of thedirections as described previously, a plurality of grating patternimages of the directions may be converted into a 2D image, and theshadow map may be generated using the 2D image. In converting theplurality of grating pattern images into the 2D image, grating patternmay be displayed in the 2D image. The grating pattern in the 2D imagemay be removed by averaging the grating pattern images, adding twointensities of the plurality of grating pattern images, of which phasedifference is 180°, or summing up intensities of some images in theN-number of images such that sum of phase differences of the imagesbecomes 360°.

It will be apparent to those skilled in the art that variousmodifications and variation can be made in the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. An inspection method for inspecting a device mounted on a substrate,comprising: projecting grating pattern light onto the substrate in aplurality of directions N-times while changing the grating pattern lightand capturing N-number of images by a camera; generating visibility mapsof the directions by using the N-number of images in each of thedirections; acquiring shadow regions of the measurement object from thevisibility maps of the directions; and merging the shadow regions of theplurality directions to generate a shadow map.
 2. The inspection methodof claim 1, further comprising inspecting the measurement object byacquiring at least one information of a size and a position of thedevice from the shadow map.
 3. The inspection method of claim 2, whereinthe visibility map (Vi(x,y)) is a ratio of amplitude (B_(i)(x,y)) toaverage (A_(i)(x,y)) (or (Vi(x,y)=Bi(x,y)/Ai(x,y))) in intensity ofimage at each pixel.
 4. The inspection method of claim 2, whereininspecting the measurement object by acquiring at least one informationof a size and a position of the device from the shadow map, comprises:comparing the shadow map and the shape template corresponding to thedevice within a specific tolerance value.
 5. The inspection method ofclaim 4, wherein comparing the shadow map and the shape template,comprises: comparing the shadow map and the template while moving theshape template from an initial position.
 6. The inspection method ofclaim 4, wherein comparing the shadow map and the shape template,comprises: multiplying a value of zero or one in the shadow template,which is allotted according to a coordinate of pixel with a value ofzero or one in the shadow map, which is allotted according a coordinateof pixel of a region where the shadow map overlaps with the shadowtemplate to get result values, and summing up the result values;determining a position where the sum of the result values becomesmaximum to be a preliminary position of the device by moving the shadowtemplate; and confirming the device is the device corresponding to theshadow template when the maximum value is no less than a criterion. 7.An inspection method, comprising: projecting grating pattern light ontothe substrate in a plurality of directions N-times while changing thegrating pattern light and capturing N-number of images by a camera;generating visibility maps of the directions by using the N-number ofimages in each of the directions (N is an integer greater than two);acquiring shadow regions of the directions from the measurement objectfrom the visibility maps of the directions; compensating the shadowregions of the directions, which are acquired; and merging the shadowregions of the directions, which are compensated, to generate a shadowmap.
 8. The inspection method of claim 7, wherein the visibility map(Vi(x,y)) is a ratio of amplitude (B_(i)(x,y)) to average (A_(i)(x,y))(or (Vi(x,y)=Bi(x,y)/Ai(x,y))) in intensity of image at each pixel. 9.The inspection method of claim 8, wherein compensating the shadowregions of the directions is performed by multiplyingamplitude((Bi(x,y)) with each pixels of the shadow region of thedirections, which is acquired.
 10. The inspection method of claim 8,wherein compensating the shadow regions of the directions, comprises:setting up a pixel of a shadow regions of the directions to be a shadowwhen the amplitude((Bi(x,y)) of the pixel is no greater than a criterionthat is previously set up.
 11. The inspection method of claim 7, furthercomprising acquiring at least one information of a size and a positionof the measurement object from the shadow map.